Smaller form factor 2.5-inch hard drives are finally getting their due in the desktop segment, and it's thanks to the rising popularity (and affordability) of all-in-one (AIO) systems. According to market research firm IHS iSuppli, worldwide shipments of 2.5-inch HDDs to all AIOs are forecast to reach about 1 million units in 2013, which doesn't sound like very much until you consider that shipments are expected to be "virtually zero" this year.

"With a maximum capacity of 1 terabyte, 2.5-inch HDDs are proving very attractive to PC makers for use in their next-generation all-in-one designs," said Fang Zhang, analyst for storage systems at IHS. "Multiple all-in-one PCs have the potential to adopt 2.5-inch HDDs, including the iMac from Apple Inc., TouchSmart from Hewlett-Packard, Series 7 from Samsung Electronics, IdeaCentre from Lenovo, Top Touchscreen from Asus Eee and all-in-one desktops from Vizio and Acer."

All-in-one (AIO) desktops will start to transition to 2.5-inch hard drives in 2013, according to IHS iSuppli.

As time goes on, 2.5-inch drives will grow in popularity, with shipments expected to increase to 3 million units in 2014 until hitting 7 million units in 2016. Traditional 3.5-inch drives will still rule the day with some 31 million units shipped in 2016, but growth will be much slower for the larger size drives, IHS iSuppli says.

There are certain advantages that 2.5-inch drives have over their 3.5-inch brethren. They're smaller, thinner, and typically consume less power, a combination that makes them increasingly attractive to slim style AIO desktops. Two disadvantages are speed and price, as most 2.5-inch drives spin at 5,400 RPM and sell for slightly more than 3.5-inch drives.